A copper-zinc alloy has the following properties:
Grain diameter (mm) Strength (MPa)
0.015 .................................. 170 MPa
0.025 .................................. 158 MPa
0.035 .................................. 151 MPa
0.050 .................................. 145 MPa
Determine
(a) The constants in the Hall-Petch equation; and
(b) The grain size required to obtain a strength of 200 MPa.