Utility Function in Consumer Credit I have been studying the area of unsecured consumer credit (consumer loans and credit cards) and credit scoring. My question is: can we have a utility function (either a lender's or borrower's utility) that can take both the borrower's credit score (probability of repayment) and loan limit (amount) as arguments in an explicit manner? What I have managed to get on the web are implicit functions of the form $f(x,y)$ e.g. on equation (1) in the article https://pdfs.semanticscholar.org/3207/55db4a277766043b5a1cb73f3b84df9cb613.pdf
Below is an example based on the general formulation in your linked article. This will very likely need a lot more fine-tuning. Moreover, the following example does not necessarily satisfy the theoretical properties laid out in footnote 16 of the paper. (You should check this.) Nevertheless I hope this could at least give you an idea of how to think about writing down an appropriate utility function that suits your purpose. 

Consider 
\begin{equation}
\Pi(d,q,\theta)=
\underbrace{\left[1+\mathrm e^{-(\alpha_0+\alpha_1 d+\alpha_2q+\alpha_3\theta)}\right]^{-1}}_{G(d,q,\theta)}
\biggl[d+\underbrace{\frac{a+bq-d}{\theta T}\left(\frac{1-(1+r)^{-\theta T}}{r}\right)^{\!\!-1}}_{M(L,q,\theta)}-q^2\biggr]\,,
\end{equation}
where


$d=$ down payment; $q=$ car quality; $\theta=$ creditworthiness; $L=$ loan amount
car with quality $q$ is priced at $p(q)=a+bq$, where $a,b$ are parameters to be estimated/calibrated
loan amount: $L=p(q)-d=a+bq-d$
probability of purchase $G(d,q,\theta)$ is modeled by a logistic distribution, which is parameterized by the variables of interest, and the $\alpha_i$'s are parameters to be estimated/calculated 
$\theta T$ is the term of the loan, which is increasing in $\theta$
assuming repayment in each period is the same, i.e. $L/\theta T$, the PV of loan payment is $M(L,q,\theta)$, where $r$ is the periodic interest rate
cost of producing a car with quality $q$ is modeled by $c(q)=q^2$