Lana Kane, Archer's spy companion, is a 70 kg pole-vaulter. She falls from a peak height of 5.90 m after pole-vaulting over a crossbar set at that height. She lands on a thick mat. When Lana first makes contact with the mat, her center of gravity is only 1.0 m high. During her impact with the mat, the mat compresses. At the point of maximum compression, Lana's vertical velocity reaches zero, and her center of gravity if only 0.5 m high. What average force did the mat exert on Lana during this impact?