'''i=input
for _ in[0]*int(i()):q=list(map(int,i().split()));print("%.2f"%(3.14159265359*abs(q[2]**2-q[5]**2)))



i=input
for _ in[0]*int(i()):*q,=map(int,i().split());print("%.2f"%(3.14159265359*abs(q[2]**2-q[5]**2)))'''


i=input
exec('*q,f=map(int,i().split());print("%.2f"%(3.14159265359*abs(q[2]**2-f**2)));'*int(i()))