Adapted from VLA p. 104 #8 (ALL IN MAPLE - Including Text Comments)

Concrete application (part 2). This problem follows up on Problem 3 from Problem Set 4. Below is the table that describes the composition of the three basic mixtures of concrete, Type S, Type A, and Type L. The corresponding vectors for these mixtures and for two custom mixtures, Type U and Type V have also been entered below.
  Super-Strong Type S   All-Purpose Type A   Long-Life Type L   Type U   Type V  
Cement 30 1812 12 18
Water 10 1010 12 10
Sand 5 2515 12 19
Gravel 5 515 12 8
Fly ash 10 28 12 5


Part A: Show that we can make the custom mix V but not the custom mix U from the three basic mixes S,A,L. Explain why just this calculation shows that {S, A, L, V} is not linearly independent, but does not say anything about the linearly independence of {S, A, L, U}.

Part B: Explain why any combination of S,A,L and V can also be achieved by a combination of just S,A, and L. In addition, show how to make the custom mix 3S +4A +2L +3V using only S,A, and L.

Part C: Show that {S,A,L,U} is a linearly independent set of vectors. What practical advantage does that have?

Part D: Define a fifth basic mix W to add to {S,A,L,U} such that any custom mixture can be expressed as a linear combination of the set of mixes {S,A,L,U,W}.

Part E: Why will there still be mixes that cannot be physically produced from this set of five basic mixes? Give an example where this happens.