Use SUMPRODUCT to calculate effort based on weighted risk probability

Since this is homework or an exam question about SUMPRODUCT, it would be inappropriate to provide a turnkey solution using SUMPRODUCT.

But let's be sure you understand the mathematical principle (probability theory), which might be your stumbling block.

First, the problem is better stated as: calculate the expected (average) hours to complete the task, based on the given "conditional probabilities".

Consider the 20 hours for the driveway. If we knew the weather would be "great", the estimated time would be 20. (Let's write 20*1. You'll understand why later.) But we don't know that. Instead, we know the probability is 0.6 (60%). So the "expected" time for "great" weather is 20*1*0.6.

Likewise, the "expected" time for good, bad, stormy and disaster weather is 20*1.1*0.25, 20*1.25*0.1, 20*1.5*0.04 and 20*2*0.01 respectively.

Thus, the total "expected" (average) time for any weather is the sum of those terms, which can be written
20*(1*0.6 + 1.1*0.25 + 1.25*0.1 + 1.5*0.04 + 2*0.01). The term between the parentheses should be reminiscent of a SUMPRODUCT calculation.

Repeat that kind of calculation for each of the landscape areas, and sum them all for the total.

It is unclear to me whether the assignment wants you to calculate the total in a single SUMPRODUCT expression, or as the sum of the individual SUMPRODUCT expressions.

It would certainly be the latter (easier) if the table at the end of your posting is part of the assignment specification, not your interpretation of it.