Write the MIPS assembly code to implement the following C code:

lock(lk)

shvar=max(shvar, x)

unlock(lk)

Assume that the address of the lk variable is in $a0, the address of the shvar variable is in $a1, and the value of variable x is in $a2. Your critical section should not contain any function calls. Use ll/sc instructions to implement the lock() operation, and the unlock() operation is simply an ordinary store instruction.