Hi there, can I get help for part B please, cannot remember how to calculate the Geometric progressions

Task 3 A lathe has to accommodate work between 25 mm and 300 mm In diameter. Given that the cutting speed is to be 25 m/min, determine the first and last spindle speeds (rev/min). You have been asked to determine a range of six spindle speeds (rev/min) for the lathe. These spindle speeds are to be arranged in: (a) arithmetic progression. (b) geometric progression. State these speeds correct to the nearest whole number. Assignment Last 3 G ) N = 1000 * 5 = 1000 x 25 = 318 rev / mm AT X D nix 25 N = 1000 * 5 1000 x 25 = 27 TXD 7 x 300 AP Speed Diameter GP Speed Diameter 27 300 22 300 85 93. 62 414 18 13 143 56 82 n4 202 39 18 67 n5 260 3 ) 193 318 28 318 25 Ap = a = 27 n6 = 318 no = a + ( n - 1 )d no a + ( n - 1 )d 318 - 27 + (n- 1) 12 : 27 + ( 2 - 1 ) d 318- 27: ( n- 12d n 2 : 27 + (1 ) 58. 2 291 = ( n .,) d 12 : 85. 2 291 2 5d 29 - d S c1= 58.2 14 : a + ( n - 1 )d 13 = a + ( n - 1 )d nu - - 2 + (4 - 1 ) 58.2 n 3 : 27 + ( 3 -1 ) 58.2 14 : 201.6 1 3 = 143. 4 15 : a + ( n - 1 )d ns: 27 (5-1)58.2 ns = 259. 8 AP Speeds are 27/, 85, 143 , 203 , 269 , 318 where are your calculations for the GP