Restriction Mapping -- Question 1

The following electrophoresis gel resulted from a study of the effects of three restriction endonucleases ( PstI,  EcoRI, and  SalI) both alone and in combination on the plasmid  pNEW. Labels above the gel indicate what went into each well; numbers to the right are the estimated sizes, in kilobases (kb), of the fragments comprising each of the bands. Your objective is to use these data to construct a restriction map for  pNEW by following the steps presented in the upper right frame of this window.