h184.56cm=tan(1.95×.25⋅1.95)=>h1=2.1589cm
h284.56+d=tan(1.95+.25⋅1.95)=>h2=.042568d+3.599557
tanθ=h14.56cm=>25.6∘
tanθ=h24.56cm+d=>tan25.6=.042568d+3.599557d+4.56cm
∴ the thickness of the lead = 3.24 cm