The phrase "a last problem" is correct and usable in written English.
It can be used when referring to the final issue or challenge in a series of problems or tasks.
Example: "Before we conclude the project, we need to address a last problem regarding the budget allocation."
Alternatives: "a final issue" or "the last challenge".
A last problem with the LB model is that it was originally developed for measuring light transmitted through a material.
The whale is included as a last problem case because it is difficult to classify without the MRCA criterion.
A last problem child is Detroit Stoker Co., which provides combustion equipment stokers, burner systems, feeders and services for heating and power generation.
A last problem is the identity of the genes which, acting on very different traits (body size, duration of development, progeny production), altogether contribute to the climatic adaptation of the populations.
Last year, I realized that Acceleration Partners (AP) had an interviewing problem the last problem I would have expected.
Mr. Levy has gotten a jump on this last problem by sitting as a trustee on the board of the School Construction Authority instead of appointing a surrogate, as previous chancellors have done.
Penguin's failed attempt to persuade an electronic crowd to co-write a novel illustrates one last problem throwing open one's organisation to electronic feedback.
In spite of a great effort, the last problem has not yet been overcome.
A solution for the last problem can be obtained by masking foreground pixels from the running mean update.
It was computed by subtracting the timestamp when a student started solving the first problem from the timestamp when a student completed the last problem in the Skill Builder.
Tye and Byrne and Hilbert have proposed a solution to this last problem, one that depends on exploiting the opponent-processing model of color vision (see section 4, above).
