From the provided options below pick the option that is most suitable.

Group of answer choices

a$.$ Coffee shops and bakeries tend to use menu $($Fixed$)$ pricing.

b$.$ Suppose a robotics firm produces and directly sells RC drones to their customers, without any intermediaries. In this case, the robotics firm$$s revenue model could be described as a $$production$-$based model$.$

c$.$ Assume that a new phone assembled by Google runs the Android OS operating system. Then the specific hardware $($the phone$)$ and operating system could be seen as possible complementary products

d$.$ a$,$ b and c$,$ are all true statements.

e$.$ a and b are true, but c is false.