One airplane is approaching an airport from the north at 206 km/hr. A second airplane approaches from the east at 157 km/hr. Find the rate at which the distance between the planes changes when the southbound plane is 27 km away from the airport and the westbound plane is 16 km from the airport.

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?