(a) Hicks & Allen, Consumer Behaviour (b) Alfred Marshall, Law of diminishing marginal utility (c) Alfred Marshall, Law of Equi Marginal Utility (d) Both (a) & (b).
In Marshall's theory, the concept of utility is cardinal. The price that a consumer is willing to pay for a good is an indication of the utility of that good to the consumer. Total utility is the sum of the utility, which a consumer derives from the consumption of the different units of a good.