As shown in figure string PQR is stretched by force F = (3 -10 Kt) N, where k is a constant and t is time in second. At time t = 0, a pulse is generated at the end P of the string. Find the value of K (in N/s) if the value of force become zero as the pulse reaches point Q.(linear density
of string is 3×10−2 kg m−1) ___