Your goal is purchases at the lowest cost. Which ad should get more budget?

Ad	Spend (£)	Clicks	CTR (%)	Purchases	CPA (£)
Ad A — Lifestyle	500	900	3.1	18	27.78
Ad B — Discount	500	620	2.2	25	20
Ad C — Testimonial	500	410	1.6	14	35.71
Ad D — Product demo	500	760	2.7	16	31.25

CPA (£)