According to a study by Dr$.$ Adam Grant and colleagues looking at a relational approach to job design, what were the results of a set of interventions involving fundraisers working at a university alumni foundation?

Only the letter intervention had effects, increasing both calls made, and donations received each week.

Interventions involving both receiving a letter from, and interpersonal contact with beneficiaries increased calls made and donations received each week.

Only the interpersonal contact intervention had effects, increasing both calls made, and donations received each week.

Only the interpersonal contact intervention had effects, increasing calls made each week, but not donations received each week