MIPS: Loading values from memory, adding them, then storing them back in memory

Question

MIPS Assembly noob here using QTSPIM

.data

  .byte 13 

  .byte 20

  .byte 150

# Add the values up, compute the average, and store the result in a memory location.

.text
.globl main


lui $10, 0x1000          #loads the starting address of the data segment.

lb $t0, 0x10 ($10)       #supposed to load 13 into $t0.

lb $t1, 0x14  ($10)      #supposed to load 20 into $t1 

add $t1, $t0, $t1        #adds the values of t0 and t1 and stores the result in t1

lb $t2,0x18   ($10)      #supposed to load 150 into $t1 
add $t1, $t1,$t2         #adds the values of t1 and t2 and stores the result in t1.

sb $t1, 0x22 ($10)       #supposed to store the result in address 0x1022, expecting
                         # result = 183 

I know i'm doing something wrong, but i'm not sure whether it's the addressing, or something else. Any help would be greatly appreciated. Thanks whenever i run the program in QTSPIM, it sometimes loads the first byte correctly, and shows "d" in register 8, but doesn't add or load anythings else correctly. when i attempt to run it again, sometimes it shows a different value (usually a hex) in the same register.

I amended the coded to:

.data

  .byte 13 

  .byte 20

  .byte 150

# Add the values up, compute the average, and store the result in a memory location.

.text
.globl main


lui $t2, 0x1000          #loads the starting address of the data segment.

lbu $t0, 0x1 ($t2)       #supposed to load 13 into $t0.

lbu $t1, 0x2 ($t2)       #supposed to load 20 into $t1 

lbu $t3, 0x3 ($t2)       #supposed to load 150 into $t3 


add $t4, $t0, $t1        #adds the values of t0 and t1 and stores the result in t1

add $t4, $t3,$t4         #adds the values of t1 and t2 and stores the result in t1.

sb $t4, 0x13 ($t2)       #supposed to store the result in address 0x1022

but i'm still getting weird undesired numbers stored in the registers.

t0=14;
t1=96;
t2=10000000 (expected);
t3=0;
t4=aa.