The standard quantity of base to be used for the sauce manufactured by Sandy's can be calculated by summing up all the given quantities. Mathematically, this can be expressed as,
Q = standard amount + allowance for waste + allowance for rejects
Substituting the known values from the given,
Q = 0.51 kg + 0.5 kg + 0.4 kg
Q = 1.41 kg
Therefore, Sandy's sauces should be able to quantify the amount of base needed for the systems and the answer to this item is equal to 1.41 kg.