If registers $t1, $t2, and $t3 all contain 3, what value will each of them contain after running the following instruction?
add $t1, $t2, $t3
a) $t1 = 3, $t2 = 3, $t3 = 6
b) $t1 = 6, $t2 = 3, $t3 = 3
c) $t1 = 3, $t2 = 6, $t3 = 3
d) $t1 = 3, $t2 = 3, $t3 = 3