Solution: First, arrange the 6 modules without restrictions: $\frac6!3!2!1! = 60$. For the constraint, note the biology lab (B) must not follow both chemistry experiments (C). Total valid arrangements: Calculate total permutations where B is not after both C's. This is equivalent to ensuring B is not in a position after both C's. Using combinatorial cases: B is first, or B is second with at least one C before it, or B is third with at least two C's before it. Alternatively, recognize that the condition excludes only $ \frac13 $ of all permutations where B is after both C's (since the C's can be ordered in 2 ways). Thus, valid arrangements: $60 - \frac13 \times 60 = 40$. The final answer is $\boxed40$. - Groen Casting