T4:
500mlX10%=50ml
m=pv=1.1g/cm3X50=55g
m=pv=1g/cm^3X500ml=500g
500g-55g=445g
H2O-------445g
NaOH------55g
T7:
15tX15%=2.25t
15tX18%=2.7t
2.25tX30=67.5t
2.7X30=81t
67.5t-----81t