$A$ screen receives $3 \ W$ of radiant flux of wavelength $6000 \ \mathring{A}.$ One lumen is equivalent to $1.5 \times 10^{-3} \ W$ of monochromatic light of wavelength $5550 \ \mathring{A}.$ If the relative luminosity for $6000 \ \mathring{A}$ is $0.685$ while that for $5550 \ \mathring{A}$ is $1.00,$ then the luminous flux of the source is:

• A
  $4 \times 10^3 \ lm$
• B
  $3 \times 10^3 \ lm$
• C
  $2 \times 10^3 \ lm$
• D
  $1.37 \times 10^3 \ lm$