The nurse in charge of the 1st floor of a senior citizen center would like to know if there is a relationship between the age of a resident (x) and the time spent per day in the care of the resident (y). For each of the 40 residents on their floor, she determines the values of x and y (in minutes). It obtains the following results:

Average age: x = 85

Average time: y = 500

Standard deviation corrected for ages: Sx = 10

Time corrected standard deviation: Sy = 100

Covariance corrected between age and time: Sxy = 750

Determine the average time (in minutes) needed to care for a resident of 80 years old.