A host must resolve the symbolic name engineering.vanderbilt.edu, the IP address of which is not known. If the name server hierarchy has 3 levels, indicate the number of DNS messages that, in the worst case, will circulate on the internet to resolve this symbolic name, if (a) a recursive resolution is used at each level, or (b) an iterative resolution. (a) 8 (b) 8. (a) 6 (b) 6. (a) 6 (b) 8. (a) 8 (b) 6. None of these answers. A host A continuously transmits data over a link with capacity R=100Mbps to a host B. Determine what is the length d of this link if its propagation speed is s=2108m/s and at most 1000 bits can be simultaneously present on the link. None of these answers. 42 2000m. 500m 1000m