Consider the following statements regarding power screws:
1. The efficiency of a self-locking screw cannot be more than 50%
2. If the friction angle is less than the helix angle of the screw, then the efficiency will be more than 50%
3. The efficiency of ACME (taperzoidal) thread is less than that of square thread.
Of these statements:
(a) 1,2 and 3 are correct
(b) 2 and 3 are correct
(c) 1 and 3 are correct
(d) 1 and 2 are correct