I REALLY NEED HELP, THIS IS "The boy in the striped pajamas" I'LL GIVE BRANLIEST

i know the whole summary ; During World War II, 8-year-old Bruno (Asa Butterfield) and his family leave Berlin to take up residence near the concentration camp where his father (David Thewlis) has just become commandant. Unhappy and lonely, he wanders out behind his house one day and finds Shmuel (Jack Scanlon), a Jewish boy of his age. Though the barbed-wire fence of the camp separates them, the boys begin a forbidden friendship, oblivious to the real nature of their surroundings.

1)a

2 b

3 d

4 d or b

explanation:

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: