b= 10x10x10x10 = 10000
c= 10x10x10x10x10x10x10x10x10x10 = 10000000000
d= 4x10x10x10x10 = 40000
2. 10^4, 3x10^4, 8x10^4, 10^7, 10^8, 10^12
3. 1/1000, 0.001; 1/100000, 0.00001; 1/100000000, 0.00000001; 1/40000, 0.0004
4. 10^-15, 10^-11, 10^-9, 1x10^-4, 6x10^-4, 10^-3