How to solve it??? Also, could you explain why the variance mean is 150 on the number.4? I thought it's 142.

Signatures 5. Measures of variation The population of cars contains the following values, in horsepower: 172, 210, 250, 400. (a) Calculate each observation's squared deviation from the population mean. (b) Use your results from (a) to find the population variance. What are its units? (c) Find the population standard deviation, report its units