b$.$ If the agent will only use the service for daytime calls, over what range of call minutes will each plan be optimal? $($Round each answer to the nearest whole number. Include the indifference point itself in each answer.$)$

Plan A is optimal from zero to

minutes. Plan $C$ is optimal from

minutes onward

c$.$ Suppose that the agent expects both daytime and evening calls. At what point $($i$.$e$.,$ percentage of total call minutes used for daytime calls$)$ would she be indifferent between plans A and B$?($Do not round intermediate calculations. Enter your answer as a percentage rounded to $2$ decimal places. Omit the $"\%"$ sign in your response.$)$

Point of indifference

percent daytime minutes