Final answer:
The topic of this question is a consumer's budget problem in Mathematics.
Step-by-step explanation:
The topic of this question is a consumer's budget problem, which is a concept in economics. It involves making choices between different goods or services based on limited income.
In this case, Deborah has a budget of $130 and she spends $78 on sushi and $52 on bagels when sushi costs $2 per piece and bagels cost $2 per bagel. Later, when the price of bagels falls to $1 per bagel, she spends $50 on sushi and $50 on bagels.