A parent is planning to have their child's birthday party at a skating rink. The deposit is $50. Each child will need to pay $3 to rent skates and $2 to rent a trainer if they want one. Write an expression that shows the total cost of the party using s for skates rented and t for trainers rented.

2s + 3t + 50
3s + 2t - 50
2s + 3t - 50
3s + 2t + 50