assembly - Runtime exception at 0x004002b0: address out of range 0x10400000 -

i'm learning mips assembly language , and i'm having issue part of program getting error "address out of range." please assist me this.

error line 294: runtime exception @ 0x004002b0: address out of range 0x10400000

    .data      filename:      .space  8      filecontents:      .space  50000      legalwords:        .space  50000      correctwords:      .space  50000         .text     importfile:     li   $v0, 13        # open file     la   $a0, filename  # load address filename     li   $a1, 0         #flags           li   $a2, 0         #mode 0: read, 1: write       syscall             # open file (file descriptor returned in $v0)     addi $sp, $sp, -4   #make room on stack     sw   $s6, 0($sp)    #save $s6 since using elsewhere     move $s6, $v0       # save file descriptor in $s6     li   $v0, 14        # system call read file     move $a0, $s6       # file descriptor      la   $a1, filecontents  # address buffer store read data     li   $a2, 500000        # maximum number of characters read     syscall             # read file     li   $v0, 16        # system call close file     move $a0, $s6       # file descriptor close     syscall             # close file     lw   $s6, 0($sp)    # restore $s6     addi $sp, $sp, 4    #restore stack    .    .    .    #fills word list until , asterix read    #a new word stored every 12 bytes.      fillwordlist:    li $a1, 0 #positon in legalwords    li $a2, 0 #currentword position counter    fillwordliststart:     lb $t0, filecontents($a0) # load current char     beq $t0, 42, fillwordlistend # found end of legalwords '*' return     beq $t0, 10, saveword #new line char found, current word loaded, go  save     sb  $t0, currentword($a2) #save character currentword     add $a2, $a2, 1 #move next position in currentword     add $a0, $a0, 1 #move next position in filecontents     j fillwordliststart          saveword:             addi $s1, $s1, 1             mul $t2, $a1, 12 #$t2 contains position in legalwords start storing currentword             li $a2, 0 #reset current word position 0             li $t4, 32 #load ' ' char $t4 resetting currentword                 savewordstart:                     lb $t3, currentword($a2) #load char @ current position                     beq $t3, 0, savewordend #reached end of current word return                     sb $t3, legalwords($t2)    #copy legalwords @ current position                     sb $t4, currentword($a2)                     add $t2, $t2, 1                     add $t3, $t3, 1                     add $a2, $a2, 1                     j savewordstart         savewordend:             li $a2, 0   #reset current word position 0             add $a1, $a1, 1 #move next position in wordlist             add $a0, $a0, 1 #move next position in filecontents             j fillwordliststart    fillwordlistend:     jr $ra       #-------------------------------end fill word   list-----------------------------------------------#  findfirstword: lb $t0, filecontents($a0) beq $t0, 10, findfirstwordreturn #branches on newline character add $a0, $a0, 1 findfirstwordreturn: add $a0, $a0, 1 move $v0, $a0   #return position of first word jr $ra  findnineletterword: beq $v0, 10, findnineletterwordreturn #nine letter word found *start of  legalwords j getlength  findnineletterwordreturn: add $a0, $a0, -11 move $v0, $a0 jr $ra          #----------------------gets length of current word in filecontents--------------------------------------------#   getlength:  li $a2, 0  #word length     getlengthstart:         lb $a1, filecontents($a0)         beq $a1, 10, getlengthend #new line char found current word length stored         add $a0, $a0, 1 #move forward 1 position in file contents         add $a2, $a2, 1 #add 1 wordlength         j getlengthstart  getlengthend: add $a0, $a0, 1 move $v0, $a2 j findnineletterword