The HMS Dreadnaught Is 40 Miles North of Montauk and Steaming

Multiple Choice

The HMS Dreadnaught is 40 miles north of Montauk and steaming due north at 20 mph, while the USS Mona Lisa is 50 miles east of Montauk and steaming due east at an even 30 mph. How fast is their distance apart increasing?

A) 88 miles per hour
B) 33 miles per hour
C) 41 miles per hour
D) 36 miles per hour
E) 72 miles per hour