Conditional Sentence

WEEKEND PLANS

Christine and Margaret are friends. They are both busy because the work and study! But on Wednesday they meet for coffee.

"What are you going to do this weekend?" asks Margaret.
"Well, I have a big project to finish for my design class. But if I can finish it by Friday, I'll do something fun as a treat," says Christine.
"That sounds great!" replies Margaret. "I think the ballet is coming to town.If it isn't too expensive, I'm going to buy tickets. Would you like to come?"
"Well, I don't really like ballet very much. If you want to go to the ballet in the evening, let's do something in the morning," says Christine.
"All right. If you have the energy, let's go swimming!" suggests Margaret.
"That sounds great! If I don't call you on Friday, send me an email at work," agrees Christine. "And if I don't answer, call me again. And if I don't pick up… oh, let's just make plans now! I'm too busy to plan later!"

source: http://www.really-learn-english.com/english-short-stories-english-conditionals-2.html