A parachutist whose mass is 60 kg drops from a helicopter hovering 2000 m above the ground and falls toward the ground under the influence of gravity. Assume that the force due to air resistance is proportional to the velocity of the parachutist, with the proportionality constant b₁ = 20 N-sec/m when the chute is closed and b₂ = 100 N-sec/m when the chute i s open. If the chute does not open until the velocity of the parachutist reaches 25 m/sec, after how many seconds will the parachutist reach the ground? Assume that the acceleration due to gravity is 9.81 m/sec². The parachutist will reach the ground after (Round to two decimal places as needed.) seconds.

A parachutist whose mass is 60 kg drops from a helicopter hovering 2000 m above the ground and falls toward the ground under the influence of gravity. Assume that the force due to air resistance is proportional to the velocity of the parachutist, with the proportionality constant b₁ = 20 N-sec/m when the chute is closed and b₂ = 100 N-sec/m when the chute i s open. If the chute does not open until the velocity of the parachutist reaches 25 m/sec, after how many seconds will the parachutist reach the ground? Assume that the acceleration due to gravity is 9.81 m/sec². The parachutist will reach the ground after (Round to two decimal places as needed.) seconds.