What is the test for eligibility for disability benefits under section 423(d)(1)(A) of the Health and Social Security Act?

To be eligible for benefits, a claimant must establish an "inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to ... last for a continuous period of not less than twelve months." 42 U.S.C. Sec. 423(d)(1)(A). When the claimant proves that she is incapable of returning to her past relevant work, the Secretary must show that there are other jobs she can perform in light of her residual functional capacity. Gonzalez v. Sullivan, 914 F.2d 1197, 1202 (9th Cir.1990).