(a) Yes. It is important to notice that this agreement is made in a commercial context. A is a trucker, B is a fleet owner and the loan of the truck is for business purposes. In commercial agreements it is likely to be inferred that the parties do intend to be legally bound.
Of course it may be possible to argue that an agreement, even if reached in a commercial context, was not intended to be binding, for example if the wider circumstances show that the particular agreement was intended to rely only on feelings of honour or friendship rather than legal enforceability. But in the absence of a clear indication to the contrary, the courts are likely to infer that commercial agreeements are intended to be legally enforceable.