Ijust need with part b and c

The depreciation per unit for a company

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

During a bike challenge riders have to collect various colored ribbons each 1/2 mile they collect a red ribbon each eighth mile they collect a green ribbon and each quarter mile they collect a blue ribbion wich colors of ribion will be collected at the 3/4 markrer