A coil of heavy flexible cable with a total length of $100 \mathrm{m}$ and a mass of $1.2 \mathrm{kg} / \mathrm{m}$ is to be laid along a straight horizontal line. The end is secured to a post at $A,$ and the cable peels off the coil and emerges through the horizontal opening in the cart as shown. The cart and drum together have a mass of $40 \mathrm{kg} .$ If the cart is moving to the right with a velocity of $2 \mathrm{m} / \mathrm{s}$ when $30 \mathrm{m}$ of cable remain in the drum and the tension in the rope at the post is $2.4 \mathrm{N},$ determine the force $P$ required to give the cart and drum an acceleration of $0.3 \mathrm{m} / \mathrm{s}^{2},$ Neglect all friction.