Let the required number of minutes = M Total minutes between 3o'clock and 6o' clock = 180 minutes M + 50 + 4M = 180 5M + 50 = 180 5M = 130 M = 26 minutes.
Because of its being pollution free and combustion efficient, Hydrogen gas is called fuel of future. Because of its origin in marshy places, Methane is called as 'Marsh Gas'.
Local replacement means that an incoming page is brought in only to the relevant process address space. Global replacement policy allows any page frame from any process to be replaced. The latter is applicable to variable partitions model only.