Help with figuring out the equations please!

A concert tour plans to advertise upcoming tour dates. The advertising budget is $60,000, and the tour manager will focus on prime time TV and Radio commercials. She would like to have between 30 and 60 radio commercials. use the table to find the number of prime time TV and radio commercials that will maximize the on-air time of the advertisements but will stay within the budget.

Table:
Type | Time(s) | Cost ($)
Radio| 20 | 400
PT TV | 30 | 1500
+ 2 other non-relevant types.

I have
x= radio
y= PT TV
x ≥ 0
y ≥ 0

Question

Help with figuring out the equations please! 

A concert tour plans to advertise upcoming tour dates. The advertising budget is $60,000, and the tour manager will focus on prime time TV and Radio commercials. She would like to have between 30 and 60 radio commercials. use the table to find the number of prime time TV and radio commercials that will maximize the on-air time of the advertisements but will stay within the budget.

Table:
Type | Time(s) | Cost ($)
Radio|    20    | 400
PT TV |  30    | 1500
+ 2 other non-relevant types.

I have 
x= radio
y= PT TV
x ≥ 0
y ≥ 0