William buys a bus ticket every day, Monday to Friday, for $2.50. The bus company has just introduced a card which can be bought to get a discount on all bus fares. Each card is valid for 4 weeks. William has worked out that he will pay exactly the same amount if he gets the card as he will if he continues to buy tickets at the normal price. Which of the following could be the price and discount for the card? A $5 for the card and a discount of 10% on ticket prices
B $5 for the card and a discount of 50% on ticket prices
C $10 for the card and a discount of 50% on ticket prices
D $10 for the card and a discount of 80% on ticket prices