$\backslash$table$[[500,60],[1,000,56],[1,500,52],[2,000,48],[2,500,44],[3,000,40],[3,500,36],[4,000,32],[4,500,28],[5,000,24],[5,500,20],[6,000,16],[6,500,12],[7,000,8],[7,500,4],[8,000,0]]$

Refer to Table $18-2.$ Assume there are two internet radio providers that operate in this market. If they are able to collude on the quantity of subscriptions that will be sold and on the price that will be charged for subscriptions, then their agreement will stipulate that

a$.$ each firm will charge a price of $$20$ and each firm will sell $3,000$ subscriptions.

b$.$ each firm will charge a price of $$32$ and each firm will sell $2,000$ subscriptions.

c$.$ each firm will charge a price of $$40$ and each firm will sell $1,500$ subscriptions.

d$.$ each firm will charge a price of $$40$ and each firm will sell $3,000$ subscriptions.