Covariance calculation tricks, question, something, calculator

Jupiter

I'm working on one of the questions in the mock exam from last year and I realized that there's no way I can solve the covariance in the exam. The calculation is really easy but it's so time consuming. Does anyone know of any tricks to calculate it? There must something i'm missing here. Is it doable on the calculator?
This goes for variance, std dev and covariance - All time-consuming calculations.
According to the CFA website, we're supposed to answer each question about 90 seconds but these questions are taking me 4-5 minutes to calculate and to make sure I have the numbers right.
Thanks