The La Costa Corporation operates five manufacturing plants in South America. The company tracks the medical costs that are directly attributed to accidents that occur at the plants each year. The following data show the medical costs (in U.S. dollars) at each plant for the most recent year along with the number of employees who work at each plant:

Medical Cost $7,400 $14,400 $12,300 $6,200 $3,100 Employees 123 402 256 109 67

a. Compute the weighted average for the annual medical costs at the five plants using the numbers of employees as the weights.

b. Explain why La Costa would want to use a weighted average in this situation rather than a simple average of the five medical cost values.