Answer is option c
Given that the cost, c(x), for a taxi ride is given by c(x) = 2x + 4.00, where x is the number of minutes.
We find that whenever 1 minute increases cost increases by 2 dollars.
Hence rate of change of cost with respect to minute of taxi ride = 2 dollas
i.e. this is of the form y=mx+b where
m =2 is the slope or rate of change and
b = 4 is the fixed charge even for 0 minute.
Thus option C is right