Change the photon rate, not the cutoff

At fixed accelerating voltage and target, the electron arrival rate is raised from 3.0 × 10¹⁵ to 7.5 × 10¹⁵ s⁻¹. Photon yield per incident electron and all target conditions are assumed unchanged.

What is the ratio of the new to the old total emitted X-ray photon rate?

Organize the givens & assumptions

Initial electron rate = 3.0 × 10¹⁵ s⁻¹
Final electron rate = 7.5 × 10¹⁵ s⁻¹

Steady operation, constant photon yield per electron; this question concerns photon production rate, not filtered detector counts.

A $0.4$
B $2.5$
C $1$
D $6.25$

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