please answer this question!

Two cars are headed for the intersection of the two roads. If Car A is travelling south at 40 km/h and car B is travelling east at 52 km/h, at what rate is the distance between the cars decreasing when car A is 4 km and car B is 5 km from the intersection? Note: Write only the numerical value of the rate, the units are already written. Write the exact answer not the decimal approximation (for example, write 1/2 but not 0.5). If the answer has a squre root then use the equation editor or use parentheses, for example, for v3 write (3)^(1/2) do not write (3)~{1/2} or (3)^[1/2]. Answer. The distance between the cars is decreasing at a rate of is km/h