Final answer:
Builder A is likely liable for the expenses of fixing the pools due to using lower-grade cement, breaching the contract and specifications, and causing the defect.
Step-by-step explanation:
The question revolves around legal liability regarding a construction defect caused by the use of lower-grade cement by Builder A. Given the information provided, Builder A is likely to be liable for the expense of fixing the pools because they used substandard materials that did not meet the agreed-upon design and specifications which resulted in the pools becoming unusable. The designing company, Builder B, and the homeowner relied upon Builder A's representation that they would build the swimming pools according to the specified standards. Thus, Builder A's decision to use lower-grade cement, leading to the defects, is a breach of contract or warranty, and possibly an act of negligence.