first with offsets:

from file1:

000c jal     computeX
0014 jal     computeY
001c jal     plocal

from file2 (add size of file1 text segment to entries from file2):

0038 lui     $at, inputX
003c ori     $t0, $at, inputX
0048 lui     $at, outputX
004c ori     $t0, $at, outputX
0064 lui     $at, inputY
0068 ori     $t0, $at, inputY
0074 lui     $at, outputY
0078 ori     $t0, $at, outputY

now with addreses (add starting address):

00400030 jal     computeX
00400038 jal     computeY
0040003c jal     plocal
0040006c lui     $at, inputX
00400070 ori     $t0, $at, inputX
00400068 lui     $at, outputX
0040006c ori     $t0, $at, outputX
00400088 lui     $at, inputY
0040008c ori     $t0, $at, inputY
00400098 lui     $at, outputY
0040009c ori     $t0, $at, outputY