A football player pushes a 590 n tackling sled. his coach observes this and believes that this is too light and wants to present the player with a greater physical challenge. he asks two players (player a weighs 100 kg and player b weighs 125 kg). the coefficient of static friction between the sled and grass is 0.70. how much force must the player exert to start the tackling sled in motion with players a and b on it