A postman needs to deliver a parcel to Peter's house 5 kilometers away from the post office. He first rides a bike for 4
kilometers, and then walks the remaining 1 km. It takes the
postman 1 hour to reach Peter's house. What is the postman's
average speed (in km/hr)?

Aheat engine that operates on a carnot cycle has an efficiency of 0.420 when its low-temperature reservoir is at 10 ∘c.part aby how many degrees celsius must you increase the temperature of the high-temperature reservoir to increase the efficiency to 0.600 if you continue to use the same low-temperature reservoir?