+6248 \(\text{If there are 8 T's there are 8 C's, so we are left with 14 slots}\\ \text{This means that A=G=7}\\ P[\text{8 T's}] = \dbinom{30}{8}\dbinom{22}{8}\dbinom{14}{7}(0.29)^7(0.23)^8(0.27)^7(0.21)^8\)
Now the problem might actually mean there are at least 8 T's. In which case we'd modify above to be
\(\large \sum \limits_{t=8}^{15}~\dbinom{30}{t}\dbinom{30-t}{t}\dbinom{30-2t}{15-t}(0.29)^{15-t}(0.23)^t(0.27)^{15-t}(0.21)^t\)
