Two questions

1.From past data, it is known that 70 percent of brand A computer users plan to buy a newer model of brand A computer in future. Suppose 25 brand A computer users are asked for their future brand preference. Use normal approximation to find the chance that exactly 10 of these users intend to switch brand in their next computer purchase.

2.Randomly select a number from the box with numbers -2,-2,-2, 0, 2, 2 and the number obtained is the amount of dollars you get. Play the game 30 times, use normal approximation to find the chance that you will be in the , losing some money.

The point is I dont know how to use normal approximation when finding exactly

Please help