Real GDP in year 10 with nominal $15 trn and price index 150 is:

Structural unemployment arises when there is a mismatch between the skills of the workforce and the demands of the job market, often due to technological changes or shifts in the economy. Since Sarah is actively seeking an engineering position, her situation does not reflect a skills mismatch but rather a choice to change careers.

Seasonal unemployment occurs due to fluctuations in demand for labor at certain times of the year, such as in agriculture or retail during holidays. Sarah's departure from the sandwich shop to seek an engineering job does not pertain to seasonal work patterns, as her motivation is based on a career change rather than seasonal labor needs.

Being "not in the labor force" refers to individuals who are neither employed nor actively seeking work, such as retirees or students. Since Sarah is actively pursuing an engineering job after quitting her sandwich shop job, she remains part of the labor force.