what bidding strategy should Tracy, a pizzeria owner, use to get more people to call her business?

Answer: for Tracy, a pizzeria owner, the bidding strategy to use is cost-per-acquisition (CPA).

Here’s how it works:
After establishing a traffic acquisition goal with an advertising partner, the advertiser sets some target CPA. If they think they can get higher conversion rates for lower bids, the initial bids are set unilaterally and then go up or down depending on performance against those targets. Advertising partners like Google let you set keyword targets and bid amounts separately. For example you could say that you want 20 clicks per day at a cost of $2 each (so $40/month) and have auto bidding adjust your nominal CPA within a range of 10% above or below this nominal price point