31. Rutte and Taborsky (2007) tested for the existence of "generalized reciprocity" in the Norway ral, Roftus norvegicus. That is, they asked whether a rat that had just been helped by a second rat would be more likely itself to help a third rat than if it had not been helped. Focal female rats were trained to pull a stick attached to a tray that produced food for their partners but not for themselves. Subsequently. each focal rat's experience was manipulated in Two treatments. Under one treatment, the ral was helped by three unfamiliar rats (who pulled the Appropriate stick). Under the other treatment, focal rats received no help from three unfamiliar rats (who did not pull the stick). Each focal rat was exposed to both treatments in random order. Afterward each focal rat's tendency to pull for an unfamiliar partner rat was measured. The number of pulls in a given period (in pulls/min.) by 19 focal female rats after both treatments is given below. After After receiving recieving Focal rat help no help 10 0.43 0.29 11 0.86 0.14 12 0.57 0.29 20 0.86 0.57 30 0.29 0.29 31 1.14 0.71 32 0.57 0.29 0.86 0.86 1.40 0.86 40 0.86 0.86 41 0.57 0.43 42 0.86 1.00 43 0.00 0.86 50 1.00 0.43 51 0.86 1.00 52 0.86 0.00 1.86 1.14 61 0.86 0.71 61 0.86 0.71 a. Draw a graph to illustrate the data. What trend is evident