For a first order reaction, the time required for completion of 90% reaction is 'x' times the half life of the reaction. The value of 'x' is

(Given : ln 10 = 2.303 and log 2 = 0.3010)

Metals generally melt at very high temperature. Amongst the following, the metal with the highest melting point will be :

Transition metal complex with highest value of crystal field splitting ($$\Delta$$₀) will be :