Correct : 2.79

Given Data
Workpiece Diameter (D) = 60 mm
Workpiece Length (L) = 400 mm
Cutting Speed (V) = 25 m min^-1
Feed (f) = 0.2 mm rev^-1
Taylor"s Constant C = 75, n = 0.25
Tool Changing Time (T_c) = 3 min
Labor and Overhead Cost = ¥5 per min
Tool Life Using Taylor"s Equation
VTⁿ = C
25 × T^0.25 = 75
T^0.25 = 3
T = 3⁴ = 81 minutes
Spindle Speed (N)
N = (1000 × V) / (π × D)
N = (1000 × 25) / (π × 60)
N ≈ 132.63 rev/min
Machining Time per Piece (T_m)
T_m = L / (f × N)
T_m = 400 / (0.2 × 132.63)
T_m ≈ 15.08 minutes
Number of Tool Changes per Piece
Tool changes per piece = T_m / T
= 15.08 / 81
= 0.1862
Tool Changing Cost per Piece
Cost = Tool changes per piece × T_c × Labor cost per min
= 0.1862 × 3 × 5
= 0.1862 × 15
= ¥2.79
✅ Tool Changing Cost per Piece = ¥2.79