Lisa leaves her house for a road trip and drives at a rate of 50 mph. keisha leaves her house 1 hour later and drives along the same route at a rate of 60 mph. at any given time t, the distance traveled can be calculated using the formula d = rt, where d represents distance and r represents rate. which system of equations can be used to find how long after lisa departs her house she is passed by keisha?
a) d=50t
d=60t-1

b) d=50t
d=60(t-1)

c) d=50t
d=59t

d) d=50(t-1)
d=60t