A and C are the only two stations on an Ethernet with data rate is 75 Mbps, the distance between station A and C is 4 km, and the propagation speed is 2\(\times\)10⁸ m/s. Station A start sending a long frame at time t₁ = 1µs; station C starts sending a long frame at time t₂ = 4.5 µs. The size of the frame is long enough to guarantee the detection of a collision by both stations. Find the time in microseconds when station A hears the collision(t3) and when station C hears the collision(t4).