Is this a good workout plan for a 15 year old?

For your info I weigh about 112 pounds and I am about 5 feet 5 inches. I mostly want to gain strength and ab muscles.

Approximate Time – 1 hour 15 minutes

Warm-Up
•Stretch – 1 minute
•Elliptical or Treadmill – 5 to 10 minutes

Exercises
•Pushups – 20
•Crunches – 20
•Jackknifes – 30
•Step Exercise – 5 reps on each leg, 2 sets
•Incline Dumbbell Chest Press – 10 reps, 2 sets
•Rear Deltoid – 10 reps, 2 sets
•Leg Extension – 5 reps on each leg, 2 sets
•Chest Press – 10 reps, 2 sets
•Leg Curl – 10 reps, 2 sets
•Pec Fly – 10 reps, 2 sets
• Medicine Ball – 20 reps, 2 sets

Cool-Down
•Treadmill – 15 minutes
•Stretch – 1 minute

I also want to add pull ups into my workout yet I do not have a bar in order to do them.

Thanks for your help in advance!