Vickers hardness: Distance between indentations

Hello, I'm writing here because I don't know how to solve this question that appeared on an exam (undergraduate, mechanical engineering). The Vickers hardness test was done on a steel plate twice, once with a smaller force and once with a larger force. The first average length of the diagonal is d=0.181 mm. The second indent (larger force was used this time) left the average length of the diagonal d=0.572 mm. What is the minimum distance between indentations? The equation we are using is B>3*d , where B is the distance between indentations, d is the average length of the diagonal. Do I just take the average value for d of 0.181 mm and 0.572 mm = 0.3765 mm? Then B>3*0.3765= 1.13 mm? I would be grateful if someone could help me with this.